1. Field of the Invention:
The present invention relates to an improvement in operational function of a matrix type gas discharge display device. The gas discharge display device to be improved in accordance with the present invention comprises an airtight container or envelope filled with gas and an electrode system sealed in the envelope. The electrode system comprises a plurality of parallel stripe shaped cathode conductors, and a number of groups of parallel wires extending normal to said cathode stripes and forming display anodes and scanning anodes to provide a matrix having rows and columns together with the cathode stripes. Each of the crossings of the rows and columns of the matrix constitutes a discharge element. The scanning anodes produce priming discharges successively at the discharge elements in a row according to an applied scanning voltage and the discharge elements successively produce display discharges according to an applied information signal voltage between the group of display anodes and said cathodes to reproduce a display picture.
2. Description of the Prior Art:
Several kinds of the matrix type gas discharge display devices are known already. In the conventional matrix type gas discharge display device not provided with the priming discharge producing mechanism, each discharge element luminates for a period Tl during which the signal voltage is applied and the period Tl is equal to a line scanning time Th for scanning a row of said matrix. This time Th is the same as a sampling period in the row direction of the picture signal to be applied simultaneously in the column direction of the matrix. In an ordinary picture display such as a display of a television picture, the field scanning (scanning in the column direction) frequency is chosen to be 50 to 100 Hz in order not to produce flickers in the displayed picture. Accordingly the field scanning period Tf which is the inverse of the scanning frequency is limited to a range of 10 to 20 milliseconds. If we assume the number of the column signal wires or the number of the wires for applying the scanning voltage in the column direction of the matrix to be m and one frame picture is formed by q field scanning by an interlaced scanning, the field scanning period Tf is given by the following equation. EQU Tf = (m/q).sup.. Th
If it is assumed that the field number q=1 for forming one frame picture and the interlaced scanning is not effected, then the one row scanning period Th is given by the above equation as follows. EQU Th = Tf/m
As can be seen clearly from the above equation, if we intend to increase the number m of the row signal wires, namely if the number of scanning lines is to be increased so as to obtain a high definition picture, then the line or row scanning period becomes shorter. This results also in a decrease of duration of illumination of each discharge element and hence the obtained picture becomes more dark.
A same disadvantage is also expected with a gas discharge display device provided with a priming discharge producing mechanism.
It has been proposed to improve such disadvantage by extending the luminating duration Tl of the display element for a period more than twice of the row scanning period Th. One such proposal is to apply the signal voltage via a time function circuit to a discharge element and to control the time of the varying signal voltage along with the time function curve before the voltage reaches the ignition voltage; the luminance is varied according to the length of the discharge time. This known system has a disadvantage in that it can be applied only to a gas discharge display device not having the priming discharge producing mechanism, so that the control of discharge duration is not stable and definite.
On the other hand it has been considered as an inevitable condition to provide said priming discharge producing function in a gas discharge display device in order to extend the discharge duration of the discharge element so as to increase the brightness of the picture to be displayed by the discharge by making an earlier rise time of the discharge. Accordingly, it is quite apparent that such a gas discharge display device having the priming discharge producing function is also desired to be improved from the aforementioned disadvantage. Furthermore, the fluctuation of starting time of discharge of the discharge elements in a gas discharge display device should be decreased to improve the influence of said fluctuation on the brightness of the displayed picture. Also the discharge of the discharge element should continue longer than a certain limit so as to increase the brightness of a discharge element.